Fetch Reject Promise With Json Error Object

When working with asynchronous JavaScript, the Fetch API is a handy tool for making network requests. But what if the server responds with an error? That's where the `fetch()` method's support for promises and the `reject` function come into play, allowing you to handle errors gracefully, along with JSON error objects.

### Understanding Fetch API

Before diving into handling errors with JSON objects, let's briefly review the Fetch API. It's a modern interface for fetching resources across the network, built into the web platform. When you make a request using `fetch()`, a Promise is returned, allowing you to process the response asynchronously.

### Handling Errors with Fetch Promise and Reject

When the server returns an error response, the `fetch()` promise is still fulfilled, but it's fulfilled with a `Response` object that represents the error. This is where the `reject` function comes in, allowing you to explicitly handle errors within your `fetch` promise chain.

Javascript

fetch('https://api.example.com/data')
  .then(response =&gt; {
    if (!response.ok) {
      return Promise.reject(response);
    }
    return response.json();
  })
  .then(data =&gt; console.log(data))
  .catch(error =&gt; console.error('Error:', error));

In the above code snippet, the `reject` function is used when the `response.ok` property is false, indicating an unsuccessful response. By rejecting the promise explicitly, the caught error is then passed down the promise chain to the `catch()` method for handling.

### Utilizing JSON Error Objects

Now, let's enhance error handling by utilizing JSON error objects, which are commonly used to provide structured error information from the server. When the server responds with a JSON error object, you can extract and handle specific error details in your code.

Javascript

fetch('https://api.example.com/data')
  .then(response =&gt; {
    if (!response.ok) {
      return response.json().then(error =&gt; {
        return Promise.reject(error);
      });
    }
    return response.json();
  })
  .then(data =&gt; console.log(data))
  .catch(error =&gt; console.error('Error:', error));

In this code snippet, we check if the response is not successful and then parse the JSON error object from the response. By explicitly rejecting the promise with the JSON error object, you gain access to detailed error information for customized error handling.

### Summary

In summary, when working with the Fetch API for making network requests in JavaScript, it's crucial to handle errors effectively. By leveraging the promise-based nature of `fetch()` along with the `reject` function, you can gracefully manage error responses from the server, especially when dealing with JSON error objects. Implementing proper error handling enhances the robustness of your applications and ensures a better user experience during network interactions.

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